I would turn down. The neighbor might be trying to work from home; he or she might be doing shift work and needs to sleep, or is maybe just a jerk, but listening to somebody practice is really annoying. Same thing over and over: even if you like that thing it's going to get annoying. I would get a modeling amp and headphones. Modern technology gets you really really close to the sound of the amp, certainly close enough for practice. Or get a good DAW and an amp sim and practice into that--you can have drums going, build backing tracks etc.